1. Field of the Invention
The present invention relates to methods for producing alcohol, and more particularly, to a method for producing allyl alcohol by hydrolysis.
2. Description of Related Art
Allyl alcohol is an important chemical intermediate for producing glycerol, medicines, perfumes, cosmetics, pesticides and the like. The allyl alcohol can also be used for producing chemical products such as epichlorohydrin, 1,4-butanediol, n-propyl alcohol, isobutyl alcohol and the like.
In the process for producing allyl alcohol via the hydrolysis of allyl acetate, since allyl acetate, allyl alcohol and water will generate azeotrope, water and esters will form two immiscible liquid phases. If a general distillation system is adopted, a plurality of separating columns including distillation, extraction and the like are required to remove allyl acetate from allyl alcohol. In such reaction system, a normal boiling point for each component and each azeotropic composition are listed in Table 1.
TABLE 1AzeotropicBoiling pointComponentcomposition wt %(° C.)Allyl acetate/Allyl alcohol/Water(75/9/16) Heterogeneous83.9Allyl acetate/Water(84/16) Heterogeneous84.0Allyl alcohol/Water(73/27) Homogeneous88.9Allyl acetate/Allyl alcohol(37/63) Homogeneous94.8Allyl alcohol—96.8Water—100.0Allyl acetate—104.3Acetic acid—118.1
In 1985, Showa Denka (a Japanese company) has developed a technique for producing allyl alcohol by the hydrolysis of allyl acetate. However, a conversion rate of allyl acetate is restricted due to the reaction equilibrium and a conventional fixed bed reactor fails to convert allyl acetate completely. Japanese Patent No. 60-237032 has disclosed a technique for recovering allyl acetate by an azeotropic distillation column and the allyl acetate after recovery can be reused by a hydrolysis reactor.
U.S. Pat. No. 8,083,903 has disclosed a modification of the above technique, whereas the process still needs at least one hydrolysis reactor, an azeotropic distillation column and a subsequent separating column. Accordingly, the process proposed by U.S. Pat. No. 8,083,903 is very complicated and energy consuming. In U.S. Pat. No. 7,041,199, Sulzer Chemtech has disclosed a method for hydrolyzing carboxylates. The method comprises steps of feeding carboxylates in a pre-reactor for hydrolysis and then feeding the mixture from the pre-reactor into a reactive distillation column. In the method, at least one pre-reactor and a reactive distillation column are needed for enhancing the conversion rate for hydrolyzing carboxylates.
However, in view of the process for producing allyl alcohol by using hydrolysis of allyl esters, there still needs to provide a simplified process and an improved conversion rate of allyl esters.